1. Field of the Invention
This invention relates to curable epoxy resins, and more particularly to epoxy resins cured with a reaction product of cyanoguanidine, amine and formaldehyde.
2. Related Publications
Cyanoguanidine is a widely used epoxy curing agent. However, it is a solid material and, therefore, difficult to use conveniently when curing liquid epoxy systems. Polyoxyalkylene amines and polyoxyalkylene polyamines are also known as epxoy curing agents. The use of cyanoguanidine (dicyandiamide) is disclosed in a technical report from American Hoechst Corporation entitled, "Dycyandiamide".
Polyoxyalkylene amines have been disclosed in many patents and publications as curing agents for epoxy resins. For example, U.S. Pat. Nos. 4,115,360; 4,141,885; 4,115,361; 4,146,700 and 4,169,177.
In the present invention it has been discovered that a reaction product of cyanoguanidine, formaldehyde and an amine, especially a polyoxyalkylene amine, provide, in most cases, a fluid, viscous liquid which is easily dispersed uniformly into epoxy resins thereby providing a new and useful epoxy resin curing agent and permits the use of cyanoguanidine in a much more usable form.